共查询到19条相似文献,搜索用时 0 毫秒
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管线钢表面裂纹体的三维断裂特性和断裂判据研究 总被引:1,自引:0,他引:1
采用中心表面裂纹试样的三点弯曲试验,研究X70管线钢表面裂纹体的断裂特性.结果表明,二维断裂力学参量KⅠ已不能客观描述和表征表面裂纹体断裂现象和裂端应力场强度.采用三维断裂力学参量KZ,能很好描述和表征表面裂纹体的试验现象和裂纹尖端应力场强度,三维断裂韧度K ZC与表面裂纹的几何尺寸和裂纹形态无关,是管线钢表面裂纹体的客观韧性指标.建立穿透裂纹和表面裂纹的统一断裂准则,即三维断裂力学准则,KZ=K FTZ≤KZC ,将该准则和失效评估图(failure assessment diagram, FAD)技术相结合,可以进行含表面裂纹管道的安全性评定. 相似文献
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《机械制造与自动化》2017,(2)
针对小裂纹断裂力学的基本概念,主要分析了油气管道表面裂纹的断裂,并运用ANSYS workbench15.0有限元软件建立裂纹的有限元模型,进行了断裂力学计算,得出了裂纹的KⅠ、KⅡ、KⅢ强度因子和J积分,定性和定量的评定了裂纹尖端的应力场强弱程度,为压力管道裂纹的研究提供了数据参考。 相似文献
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基于有限元方法的裂纹扩展寿命预测 总被引:2,自引:1,他引:1
采用有限元方法确定结构的断裂力学参量,并与标准紧凑拉伸试样(compact tension,CT)的理论值相比较,结果表明有限元方法确定结构的断裂力学参量是可行的.以真实构件发动机涡轮盘为例,首先进行该结构的断裂力学分析;然后进行二次开发模拟构件的裂纹扩展,计算断裂力学参量,拟合出其与裂纹长度的函数关系,确定涡轮盘的临界裂纹长度;最后,选取试验确定的疲劳裂纹扩展率模型,完成构件的裂纹扩展寿命预测,通过与试验检测的结果相对比,证明基于有限元方法的裂纹扩展寿命预测是合理有效的. 相似文献
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31Si2MnCrMoVE钢是为符合固体火箭发动机壳体设计需要而专门研制的超高强度钢.随着冶炼技术的进步,31Si2MnCrMoVE钢断裂韧度不断提高,构件采用的板厚也越来越薄.由于较高的断裂韧度和较小的板厚,给钢板表面裂纹断裂韧度测试带来困难,韧带尺寸偏小,难以满足有效性判据.这种情况下,不应该用线弹性断裂力学方法评价材料的断裂韧度,而应采用弹塑性断裂力学测试材料的延性断裂韧度JIC.基于以上原因,在条件断裂韧度不满足有效性判据的情况下,采用试验与有限元分析相结合的方法,通过试验测出裂纹启裂时的条件载荷,用有限元法计算出在条件载荷作用下的延性断裂韧度JIC,再用断裂力学理论转换成表面裂纹断裂韧度KIe.用JIC作为断裂参量,就必须分析J积分的有效性,因此讨论超高强度钢表面裂纹前缘的J守恒和J主导的有效性,从而为固体火箭发动机设计提供依据. 相似文献
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在小范围屈服条件下,断裂韧性的临界值(Kc、δc、Jc)与试件几何形状无关,能反映材料的固有特性。但在大范围屈服条件下,研究结果表明[1~6]:由于试件几何尺寸所造成的裂纹尖端拘束状态的差异,导致Jc、δc值与试件几何形状相关,如深缺口试件的断裂韧性值比浅缺口试件低,拉伸试件的断裂韧性值较三点弯曲试件高。近来提出了两种研究裂纹尖端拘束状态对断裂韧性影响的方法。一种是用T—应力或Q参量来定量描述裂纹尖端应力场的J—T和J—Q理论;另一种是基于概率断裂力学的方法——局部法[6、7],采用考虑裂纹尖端… 相似文献
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采用三点弯曲试样对APIX52管线钢焊接接头母材金属区断裂韧度COD特征值进行了测试研究。研究结果表明,焊缝金属的力学性能对母材金属的起裂韧工,裂纹扩展阻力,撕裂模量及延伸区宽度有很大的影响,其影响程度取决于裂纹离焊缝的距离,离焊缝愈近,影响愈大,裂纹尖端的延伸区宽度和起裂韧度具有良好的线性关系。 相似文献
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The reliable stress intensity factor analysis is required for fracture mechanics design or safety evaluation of mechanical joints at which cracks often initiate and grow. It has been reported that cracks in mechanical joints usually nucleate as corner cracks at the faying surface of joints and grow as elliptical arc through cracks, In this paper, three dimensional finite element analyses are performed for elliptical arc through cracks in mechanical joints. Thereafter stress intensity factors along elliptical crack front including two surface points are determined by the virtual crack closure technique. Virtual crack closure technique is a method to calculate stress intensity factor using the finite element analysis and can be applied to non-orthogonal mesh. As a result, the effects of clearance on the stress intensity factor are investigated and crack shape are then predicted. 相似文献
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含卡瓦作业损伤钻柱的适用性评价研究 总被引:2,自引:0,他引:2
针对卡瓦在钻柱表面上留下的作业损伤对钻柱断裂失效有严重影响的问题,提出一套系统的卡瓦作业损伤对钻柱断裂失效影响的评价方法。以卡瓦内悬挂钻柱的受力分析及卡瓦对钻柱损伤的弹塑性力学分析为基础,建立卡瓦对钻柱的损伤模型;基于断裂力学理论,推导卡瓦作业损伤对钻柱断裂失效的评价参数,并且将钻柱的工作载荷、断裂韧性和缺陷尺寸(卡瓦作业损伤)三者紧密的联系起来评价含卡瓦作业损伤钻柱的适用性。根据理论分析,建立适合油田人员参考的含卡瓦作业损伤钻柱失效评价曲线图,并提出含卡瓦作业损伤钻柱的三级评定方法,为油田安全操作提供有效参考。 相似文献
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采用 MARC有限元程序提供的 Delorenzi虚拟裂纹扩展方法计算了平面应力条件下不同强度匹配的焊缝纵向受载的含横向裂纹的焊接接头在不同载荷的广义 J积分。计算结果表明 :力学不均匀性对含横向裂纹焊接接头的 J积分有重要影响 ,低匹配焊接接头中积分路径穿越焊缝与母材界面的 J积分值高于积分路径在焊缝内的 J积分值 ,高匹配焊接接头中积分路径穿越焊缝与母材界面的 J积分值低于积分路径在焊缝内的 J积分值 ;载荷越大 ,焊缝与母材的强度差别越大 ;积分路径中包含的焊缝与母材界面长度越大 ,J积分的差值越大。力学不均匀性对焊缝纵向受载的含横向裂纹的焊接接头 J积分的影响是由焊缝与母材的强度差别及积分路径中包含的焊缝与母材界面长度的不同造成的 相似文献
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SS400钢是一种超细晶粒、超纯净、具有优良综合力学性能的新一代钢铁材料,其焊接结构性能的研究对其推广应用具有重要的意义。文中通过数值分析方法,以SS400母材性能为参照,对其实际焊接接头的抗断裂性能进行评估。采用MARC商用软件,对不同中心贯穿裂纹尺寸的SS400母材及其实际焊接接头拉伸板模型进行三维有限元计算和拉伸过程模拟。焊接方法为脉冲熔化极混合气体保护焊,焊接板的中心裂纹处于焊缝与热影响区之间的熔合区。用作比较的母材板的裂纹尺寸和位置、网格划分、边界条件等与焊接板完全相同。根据计算结果,分析焊接接头力学不均匀性对应力应变场的影响,并依据全面屈服理论对断裂参量CTOD进行分析比较。结果表明,焊接接头的CTOD值均低于同裂纹尺寸的纯母材。因此,该焊接接头拉伸板的抗断性能应优于纯母材。 相似文献
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A study on the fatigue life prediction of tire belt-layers using probabilistic method 总被引:1,自引:0,他引:1
Dongwoo Lee Seongrae Kim Kideug Sung Jongsang Park Taewon Lee Sunchul Huh 《Journal of Mechanical Science and Technology》2013,27(3):673-678
Tire belt separation failure is occurred by internal cracks generated in #1 and #2 belt layers and by its growth. And belt failure seriously affects tire endurance. Therefore, to improve the tire endurance, it is necessary to analyze tire crack growth behavior and predict fatigue life. Generally, the prediction of tire endurance is performed by the experimental method using tire test machine. But it takes much cost and time to perform experiment. In this paper, to predict tire fatigue life, we applied deterministic fracture mechanics approach, based on finite element analysis. Also, probabilistic analysis method based on statistics using Monte Carlo simulation is presented. Above mentioned two methods include a global-local finite element analysis to provide the detail necessary to model explicitly an internal crack and calculate the J-integral for tire life prediction. 相似文献
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Seung Hoon Nahm Hae Moo Lee Chang Min Suh 《Journal of Mechanical Science and Technology》1996,10(4):396-404
A new experimental system using remote measurement system (RMS) and image processing technique was applied for studying the growth behavior of small surface fatigue cracks in 1Cr ?1Mo?0.25V steel at room temperature. The system includes a long distance focusing microscope, a CCD camera, a light source, a 3-axis controller a monitor, a personal computer and a data translation card. The measurement error of the system appeared to be 0.8%. It is possible for this system to measure down to 30 μm of surface fatigue crack length. The length of surface fatigue crack could be successfully measured by the RMS during testing as well as after the test. The growth rate of small cracks on smooth specimens was represented in terms of stress intensity factor and J-integral. At equivalent elastic stress intensity factor levels, the growth rate of small surface cracks was not consistent and faster than that of long crack of CT specimen. 相似文献